The primary objectives of this protocol are to 1) determine the efficacy and safety of intravitreous aflibercept injections versus sham injections (observation) for prevention of PDR or CI-DME in eyes at high risk for development of these complications and 2) compare long-term visual outcomes in eyes that receive anti-VEGF therapy early in the course of disease with those that are observed initially, and treated only if high-risk PDR or CI-DME with vision loss develops.